Process of photochemical reforming of plastics using a carbon enabler

Abstract

A photochemical process for converting plastics into hydrogen, monomers and oligomers using a light-absorbing carbon enabler in a reactor under ambient conditions is disclosed.

Description

PROCESS OF PHOTOCHEMICAL REFORMING OF PLASTICS USING A CARBONENABLERFIELD OF INVENTION

[0001] The present invention relates to methods for catalytic decomposition of plastic waste and hydrogen production.BACKGROUND OF INVENTION

[0002] Plastic waste is an environmental concern. Diversion of plastic waste from landfills is hindered by challenges in recycling plastic waste. Thermoplastics such as polyvinylchloride, polystyrene, and polyurethane make up nearly 20% of all plastics used. However, these high-use thermoplastics are not recycled due to the resulting emission of dangerous substances and low cost-effectiveness because of low densities and high viscosities. Mixed plastic waste is also difficult to recycle due to unwanted products generated during traditional recycling processes.

[0003] Mechanical recycling dominates current recycling practices due to its low cost and technological requirements. Plastic waste from municipal outputs generally contain unsorted mixed plastic types, which need to be separated before recycling.Separation of these plastic wastes is incredibly difficult. Generally, mechanical recycling occurs via the following steps: 1 ) washing to remove bio-organic materials such as food waste and paper, 2) shredding / grinding of plastic into smaller more manageable pieces, followed by 3) melting and recasting of the polymer, often with virgin material to tune properties such as rigidity and strength, into new products. However, this process is hampered by end-product degradation compared to the virgin polymer. Furthermore, chemical degradation under the heat and mechanical stress characteristic ofmechanical recycling means that mechanically recycled plastic is generally not considered food-safe. Thus, the lifetime of recycled plastics via mechanical methods is limited due to harsh grinding, heating, and extrusion steps. As well, plastic composites are often unsuitable for recycling as they produce immiscible end-products with inconsistent mechanical properties. Mechanical recycling is also limited to thermoplastic waste feedstocks, which are pliable and can be reformed with heat; the other category is thermoset plastic, which only bums when heated, making them unsuitable for mechanical recycling.

[0004] Chemical recycling, or the breakdown of waste feedstock into smaller functional components, is an alternative to traditional mechanical recycling that forgoes many of its downsides. Of the chemical recycling methods, pyrolysis, which is the thermally induced breakdown of long chains into smaller parts in the absence of oxygen, is the simplest. The process’s simplicity, cost effectiveness, and disregard for sorted over unsorted waste make it an attractive option for liquid fuel generation from plastic wastes, with some reports claiming 80% conversion by weight from plastic into liquid oil, with the rest being char or gaseous products such as small molecular weight (MW) hydrocarbons (HCs) and hydrogen. However, like many thermal processes, pyrolysis suffers from large energy demands and safety concerns associated with maintaining the high temperatures needed for the reaction, where some processes demand over 800°C to prevent the formation of unwanted products. These processes are highly energy-and-carbon-emission-intensive, and the high temperatures required can only be sustained by the combustion of fossil fuels.

[0005] Similarly, gasification is the breakdown of feedstock through heating, the difference being the addition of an oxidizer. The process generally produces syngas, which is a mixture of carbon monoxide and hydrogen, and methanol, which are less valuable than unoxidized HCs.

[0006] Chemolysis is the breakdown of wastes using various reagents to essentially reverse the polymerization process. The process is limited to specific polymers, such as polycaprolactones, nylons, and polyethylene terephthalate. Chemolysis has the benefit of creating food-safe plastics identical to the virgin material but comes at the cost of needing more reagents (eg. water or glycol), which creates additional monetary and logistical expenses. Thus, plastics from chemolysis are often more expensive than their virgin counterparts, making the process not economically viable with current technologies.

[0007] Photoreformation, or the use of light to break waste material into smaller parts, are being researched for waste plastic degradation. Past studies on plastic reformation using light generally employed transition metal oxide catalysts to improve photo-generated electron conductivity and / or light absorption. For example, CdS / CdOx quantum dot systems have been investigated by llekert, T. et al. Energy Environ Sci 2018, 11 (10), 2853-2857 for photoreforming of polylactic acid (PLA), polyethylene terephthalate (PET), and polyurethane (Pll) but were hindered by catalyst toxicity and high cost.

[0008] Carbon nitride (CNx), carbon nanotubes (CNT), and nickel-based systems have also been shown by llekert, T. et al. J Am Chem Soc 2019, 141 (38), 15201 -15210 to increase H2 production during plastic photoreformation. However, this systemrequired another reagent, triethanolamine, as a consumable electron donor, which increases operation cost in large-scale implementations.

[0009] NiMo nanoparticles have been used by Gong, X et al. Appl Catal B 2022, 307, 121143 on a substrate of graphitic CNx and carbon nanotubes to dehydrogenate PET and PLA, but it hindered by high catalyst complexity and a tendency to decompose under high temperatures.

[0010] Thus, catalyst toxicity, high cost, complex process steps, catalyst complexity, stability, and commercial scalability are difficulties with photoreforming of plastic waste.SUMMARY OF THE INVENTION

[0011] According to an embodiment of the invention, a process for reforming plastic waste to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers is provided. The process comprises introducing a plastic from plastic waste into a reactor containing a light-absorbing carbon enabler; exposing the light-absorbing carbon enabler in the reactor to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; optionally, separating the hydrogen from one or more coproducts of the reaction; and optionally, separating oligomers from one or more coproducts of the reaction.

[0012] According to another embodiment of the invention, a process for reforming plastic waste in a reactor is provided. The process comprises the steps of: depositing a light absorbing carbon enabler onto a thermally and light resistant substrate in thereactor; depositing a plastic from plastic waste to contact the light absorbing carbon enabler; exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; optionally, separating the hydrogen from one or more co-products of the reaction; and optionally, separating oligomers from one or more co-products of the reaction.

[0013] According to another embodiment of the invention, a process for reforming plastic waste is provided. The process comprises the steps of: mixing a plastic from plastic waste and a light absorbing carbon enabler to form a mixture; introducing the mixture into a reactor; exposing the mixture in the reactor to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; optionally, separating the hydrogen from one or more co-products of the reaction; and optionally, separating oligomers from one or more co-products of the reaction.

[0014] According to another embodiment of the invention, a process for photoreforming plastic waste in a reactor containing a light absorbing carbon enabler is provided. The process comprises the steps of: introducing a plastic from plastic waste into the reactor; mixing the plastic from plastic waste and the light absorbing carbon enabler to form a mixture; exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas,monomers and oligomers; optionally, separating the hydrogen from one or more coproducts of the reaction; optionally, separating oligomers from one or more co-products of the reaction.

[0015] According to another embodiment of the invention, a process for photoreforming plastic waste in a reactor containing a light absorbing carbon enabler is provided. The process comprises the steps of: arranging the light absorbing carbon enabler into sheets by pressing or embedding the carbon enabler into a thermally and light resistant substrate; depositing a plastic from plastic waste to contact the light absorbing carbon enabler; exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; optionally, separating the hydrogen from one or more coproducts of the reaction; and optionally, separating oligomers from one or more coproducts of the reaction.

[0016] According to certain aspects of the invention, the plastic comprises a pure olefinic plastic or a mixture of different olefinic plastics. The pure olefinic plastic may be polyethylene, polypropylene, polybutylene, polystyrene, polymethylpentene, all isomers of polyethylene, all isomers of polypropylene, all isomers of polybutylene, all isomers of polymethylpentene, co-polymers thereof, or mixtures thereof. The mixture of olefinic plastics may comprise two or more of polyethylene, polypropylene, polybutylenes, or polystyrenes.

[0017] According to another aspect of the invention, the oligomers are shortchain oligomers, such as methane, ethane, propane, butane, pentane, hexane, and their unsaturated derivatives, saturated isomers or unsaturated isomers thereof.

[0018] According to another aspect of the invention, the plastic is in the form of film, powder, pellets, fibers, micro-particles, nano-particles, or combinations thereof. The plastic may be pelletized or shredded.

[0019] According to another aspect of the invention, a mass ratio of the light absorbing carbon enabler to the plastic is between 1 :1 to 1 :1000.

[0020] According to another aspect of the invention, the light absorbing carbon enabler comprises coal, biomass, carbon black, single walled carbon nanotubes, multi walled carbon nanotubes, biochar, graphene, or graphite. The light absorbing carbon enabler may be carbon black.

[0021] According to another aspect of the invention, the light source is located inside the reactor, or outside the reactor. The light source may comprise solar light, a Xenon light source, a light emitting diode (LED) light source, or by other artificial light sources.

[0022] According to another aspect of the invention, the photoreforming of the plastic is carried out under a light intensity ranging from about 5 suns to about 10,000 suns, or less than 100 suns. The photoreforming of the plastic may be carried out under a light intensity ranging from about 0.5 W / cm2to about 50 W / cm2

[0023] According to another aspect of the invention, the reactor is a continuous stirred reactor or batch reactor.

[0024] According to another aspect of the invention, the process is free from hydrogen, water, or solvents as co-reactants.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following drawings are only for the purpose of illustrating one or more embodiments of the present invention and are not to be construed as limiting the invention. They may be used to understand the processes described herein and the results of the experimental work discussed below.

[0026] Figure 1 is a graph showing relative production rates of hydrogen, monomers, and oligomers from polyethylene under various conditions.

[0027] Figure 2 is a graph showing production rates of hydrogen from polyethylene under various conditions.

[0028] Figure 3 is a graph showing product distribution of hydrogen, monomers, and oligomers from polyethylene over irradiation time.DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention provides a non-toxic, simple and low-cost process for catalytic decomposition of plastic waste to produce hydrogen and valuable shortchain oligomers. A light absorbing carbon enabler and a light energy source are used under ambient conditions to decompose plastic waste into hydrogen, monomers, and oligomers. In the use of the present invention, the toxic, complex and high-cost prior art methods can be avoided by the use of a low-cost, non-toxic and renewable light absorbing carbon enabler in the presence of light to decompose plastic waste to produce hydrogen and valuable short-chain oligomers.

[0030] Compared to current predominant mechanical plastic recycling methods, the process produces products of higher value and purity (hydrogen gas and waste plastic feedstock oligomers) and allows the carbon in the recycled material to be continuously reused compared to current mechanical recycling methods in which the recycled plastic has a finite number of times in which it can be recycled. Mixed-olefinic plastic wastes which cannot easily be used directly in mechanical recycling. The present invention permits taking mixed-feed olefinic plastic wastes and generates valuable short-chain oligomers and hydrogen gas, which can be used for other chemical reactions or made into new virgin-quality plastic. Examples of short-chain oligomers are methane, ethane, propane, butane, pentane, hexane, and their unsaturated derivatives and saturated or unsaturated isomers, such as but not limited to ethylene, propylene, butylene, pentene, hexene, and ethyne, propyne, butyne, pentyne, and hexyne. This circumvents the high waste feedstock separation costs associated with traditional recycling methods while producing higher quality and value end-product.

[0031] The photoreforming process described herein can also be more energy efficient than comparable chemical recycling methods, such as high temperature pyrolysis, which requires temperatures several hundred degrees higher than the described process with light. Additionally, carbon-enabled photoreforming requires no additional energy other than from a light source. As well, no additional solvents or feedstocks are required other than the described plastic wastes. These characteristics combined with the low cost and environmental footprint of the carbon enabler increase plastic recycling’s energy efficiency, lower process and product cost, and minimize environmental impact.

[0032] In an embodiment of the present invention, plastic from plastic waste is photo reformed by exposing the plastic to a light source in the presence of a light absorbing carbon enabler dispersed on a substrate resulting in the decomposition of plastic waste, and production of hydrogen, monomers and oligomers.

[0033] In another embodiment of the present invention, plastic from plastic waste is mixed with the light absorbing carbon enabler to bring the plastic waste in contact with the light absorbing carbon enabler. The mixture is exposed to a light energy source in a reactor, which may be a batch reactor or a continuous stirred reactor, under ambient conditions resulting in the decomposition of plastic waste, and generation of hydrogen and a product from the plastic waste, which may be monomers or oligomers from the plastic waste.

[0034] In some embodiments of the present invention, the light absorbing carbon enabler is dispersed onto a thermally and light resistant substrate in the reactor. In other embodiments, the light absorbing carbon enabler is arranged into sheets by pressing or embedding the carbon enabler into a thermally and light resistant substrate.

[0035] Plastic from the plastic waste may be in the form of film, powder, pellets, fibers, micro-particles, nano-particles, or combinations thereof. Preferably, the plastic is pelletized or shredded to facilitate better mixing.

[0036] The plastic may have low, medium, or high molecular weight. The plastic may be a pure olefinic plastic or a mixture of different olefinic plastics. Examples of suitable olefinic plastics include, but are not limited to polyethylene and all isomers thereof, polypropylene and all isomers thereof, polybutylene and all isomers thereof, polystyrene, polymethylpentene and all isomers thereof, co-polymers thereof, ormixtures thereof. Co-polymers may include the co-polymerization of poly-a-olefins and addition of plasticizers and other additives.

[0037] The mass ratio between the carbon enabler and the plastic can be 1 :1 to 1 :1000.

[0038] The purpose of the light absorbing carbon enabler is to decompose the plastic from the plastic waste into hydrogen, monomers and oligomers.

[0039] The light absorbing carbon enabler of the present invention includes, but is not limited to coal, biomass, carbon black, multi carbon nanotubes, single carbon nanotubes, biochar, graphene, and graphite, in addition to any of their doped variants (i.e. by addition of metal nanoparticles, single atoms, or substitution with non-metals). In some embodiments, the carbon enabler is carbon black. These carbon materials can be functionalized with single metal atoms or metal nanoparticles or doped with non- metals during the interface of the light absorbing carbon enabler and plastic waste.

[0040] In another embodiment, the carbon enabler can be arranged into sheets either by pressing or embedded into a thermally and light resistant substrate, such as but not limited to metal, ceramic or glass, which are introduced in the reactor. Then, plastic waste is added on top and melted by external heating to achieve good contact with the enabler. Then, the sheet containing the plastic waste can be irradiated by passing it under a sufficiently strong light source. Off gases can be continuously collected and the solid portion separated for use.

[0041] The purpose of mixing plastic from plastic waste with the light absorbing carbon enabler is to bring the plastic waste in contact with the light absorbing carbon enabler. The mixing step is solvent-free and may be carried out in a batch-type systemprior to introduction into the reactor. Alternatively, the plastic from plastic waste and the light absorbing carbon enabler may be introduced into a reactor, and mixed in the reactor prior to irradiation. In one embodiment, the reactor is a batch-type stirred tank reactor, such as but not limited to a stirred tank with a window through which light can penetrate the enabler and plastic mixture. The reactor can be heated or unheated by way of additional heaters, such as but not limited to resistive heating or heat exchange from fossil fuel combustion. Plastic and carbon enabler may be mixed in the stirred tank reactor by ways of a propellor. Off-gases may be continuously collected or collected at the end after the plastic has been converted to the desired state.

[0042] The light energy can be from artificial and / or natural sources, such as solar light, a Xenon light source, light emitting diode (LED) light source, or other artificial light source. The light source may be located within or outside of the reactor. The light source may be single, multiple, or continuous wavelengths ranging from the ultraviolet to infrared. The intensity of the light source may range from about 5 suns (or 5 kW / m2) to about 10,000 suns(or 10,000 kW / m2), and preferably below 100 suns (or 100 kW / m2). In some embodiments, the light intensity may also range from about 0.5 to about 50 W cm2, or from about 10 to about 50 W cm2. The intensity of the light may be adjusted by optical or electronic means, such as by the use of lenses, or by adjusting the power to the xenon, LED, or other artificial lighting used. The reaction mixture should be irradiated for sufficient time so that the desired product mixture is achieved. Use of light energy together with the use of one or more light absorbing carbon enablers can catalyze the decomposition of polymers into hydrogen gas and valuable monomers andoligomers at lower temperatures than those required in the prior art, with consequent lower energy consumption.

[0043] Artificial lighting used in the process of the present invention may be powered by renewable energy. In one embodiment, LEDs operate 24-7. In another embodiment, LEDs may be combined intermittently with solar irradiation during nondaylight hours. Thus, the process can be driven using solar light during daylight hours and LEDs during non-daylight hours to allow the process to run continuously. Compared to traditional thermal strategies, using solar energy, or artificial light generated from renewable energy, to trigger reformation of plastics can break the thermodynamic limitation and access the reactions at milder conditions, as well as to mitigate greenhouse gas emissions.

[0044] The process of the present invention may be carried out at ambient temperatures, such as temperatures as low as 20 degrees Celsius, although the rate of production of hydrogen may increase as temperatures in the reactor are increased, Notwithstanding this, the use of light and light absorbing carbon enablers permits the generation of hydrogen at temperatures substantially lower than those of the prior art.

[0045] The process of the present invention may be carried out in a continuous stirred reactor, batch reactor or flow process at pressures from about ambient pressure to 30 psi, or at other pressures within the skill and knowledge of a person skilled in the art.

[0046] The mixture is irradiated with an appropriate intensity of light so that the reaction can start. The reactor should be mixed continuously for even reaction as light- driven reactions only occur on the irradiated interfaces between enabler and reactant.Optionally, additional heating may be utilized to kickstart the melting of plastic to ensure greater enabler / reactant contact and increase rate of reaction.

[0047] To demonstrate I determine the utility of the process of the present invention in reforming plastics, plastic pellets were contacted with a light absorbing carbon enabler in a reactor, as described in more detail in the following examples. Light absorbing Carbon Enabler & Plastic

[0048] Ultra-pure carbon black (CB) from acetylene combustion (Alfa Aesar; CAS: 1333-86-4, ash content 0.016%) and low-density polyethylene (LDPE) pellets (Dow Inc; ASPUNTM 6834 Fiber Resin) were used for all reactions.Reactor

[0049] The reactor comprised a stainless steel reactor body with one or more guartz glass windows disposed on its circumference, and valves controlling the inflow and outflow of gas to and from the reactor body. The guartz glass windows in the reactor allowed light, which could be solar, or LED or Xenon lighting, simulating solar light, to irradiate the surface of the light absorbing carbon enablers in the plastic mixture placed within the reactor and to promote the decomposition of plastic and generation of reaction products in the reactor. The reactor may be heated by way of, for example, a heating cartridge located inside or outside the reactor body.

[0050] Either solar power, magnified by the use of optical lenses, Xenon lighting, or four combined or separated LED lights (UV, blue, green and red) were used as the light source for the reaction. Manually varying the power to the Xenon or LED lights yielded varying light intensities. An OMEGA temperature controller was attached to aheating cartridge inserted into a copper block along with a thermocouple inserted into the reactor for measuring and controlling the temperature in the reactor.Example 1: Carbon-Enabled Photoreforming of Plastics to Useful Reaction Products under Ambient Conditions

[0051] To confirm the utility of the photochemical process, various conditions were used to determine the photoresponsivity of polyethylene. Ultra-pure carbon black (CB) from acetylene combustion (Alfa Aesar; CAS: 1333-86-4, ash content 0.016%) and low-density polyethylene (LDPE) pellets (Dow Inc; ASPUNTM 6834 Fiber Resin) were used for all reactions. The relative production rates of reaction products from the photoreforming of polyethylene was compared to as compared to “dark” conditions with and without the carbon enabler.Thermal Tests

[0052] Three thermal tests were conducted under “dark” conditions at the reactor and drive by temperatures from 250-550 °C shown in Figure 1. All thermal tests were conducted in a 16.7 by 1 cm borosilicate glass test tube batch reactor inset into an external heater. 0.73 g of LDPE pellets were either placed alone or with 0.16 g of carbon black into test tube reactor every run. Air in the system was vacuumed before filling with 17 psi of Ar to purge oxygen from the reaction mixture. Reactors were heated up to described temperatures Figure 1 for 1 hr before cooling and analyzing gaseous products in the top of the tube by GC-FID / TCD.

[0053] Reference reactions were conducted at the same temperatures using onlyLDPE in the test tube reactor to determine the rate of spontaneous LDPE decomposition.

[0054] Reactors were allowed to cool to room temperature before gas analysis by GC detection methods.Photoactivity Tests

[0055] Light reactions to observe the photoreforming of polyethylene was conducted under ambient conditions without the addition of heat. . All photoactivity tests were conducted under Ar or Ar / hexanes atmosphere.

[0056] Approximately 0.06 g of CB was pressed into a thin layer around 1 mm thick at the bottom of a 1 .6 cm diameter borosilicate glass cup placed within an 8.7 mL stainless-steel batch reactor with a quartz glass window. Approximately 0.3 g of LDPE pellets were then placed evenly over the CB layer. The reactor was then sealed, air was removed by vacuum, and replaced with 23 psi of Ar. Circular test areas with a diameter of 1 .2 cm were irradiated with a Xe lamp at 8.25 W / cm2for set time intervals (1 hour for Figure 1 ; 10, 30, and 60 m inutes for Figure 3). The reactor was then allowed to cool before gaseous products were collected and analyzed by GC-FID and GC-TCD.

[0057] Photoactivity tests were also conducted on CB and LDPE separately to determine standalone contributions.

[0058] Figure 2 shows the hydrogen generation rate from the photoreforming of polyethylene with the light absorbing carbon enabler as compared to “dark” conditions.

[0059] The light absorbing carbon enabler was demonstrated to have little effect under dark conditions for plastic reforming. In contrast, reactions conducted under light conditions without external heating exhibited incredibly high plastic photoreforming rates on the scale of a million times greater than under dark conditions at the same surface temperature.

[0060] These results demonstrated that the use of light energy together with the use of one or more light absorbing carbon enablers is significantly more effective at catalyzing the decomposition of polymers into hydrogen gas and valuable monomers and oligomers at lower temperatures.Example 2: Reaction Product Distribution over Irradiation Time

[0061] To evaluate the reaction product distribution based on irradiation time, various conditions were used to determine the photoresponsivity of polyethylene.

[0062] Figure 3 shows the distribution of reaction products in a batch reactor from the photoreforming of polyethylene according to the process described in Example 1 which was evaluated at intervals of 10 minutes, 30 minutes and 60 minutes.

[0063] These results demonstrated that longer irradiation times result in greater proportions of shorter-chain oligomers.

[0064] While the embodiments of the present disclosure have been described in detail, it is to be understood that, unless otherwise specified, the present disclosure is not limited to particular materials, reaction materials, processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequences where this is logically possible.

Claims

CLAIMS1 . A process for reforming plastic waste to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers, the process comprising a. introducing a plastic from plastic waste into a reactor containing a lightabsorbing carbon enabler; b. exposing the light-absorbing carbon enabler in the reactor to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce the mixture of reaction products comprising hydrogen gas, monomers and oligomers; c. optionally, separating the hydrogen from one or more co-products of the reaction; and d. optionally, separating oligomers from one or more co-products of the reaction.

2. A process for reforming plastic waste in a reactor, the process comprising the steps of: a. dispersing a light absorbing carbon enabler onto a thermally and light resistant substrate in the reactor; b. depositing a plastic from plastic waste to contact the light absorbing carbon enabler; c. exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to reactwith each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; d. optionally, separating the hydrogen from one or more co-products of the reaction; and e. optionally, separating oligomers from one or more co-products of the reaction.

3. A process for reforming plastic waste, the process comprising the steps of: a. mixing a plastic from plastic waste and a light absorbing carbon enabler to form a mixture; b. introducing the mixture into a reactor; c. exposing the mixture in the reactor to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; d. optionally, separating the hydrogen from one or more co-products of the reaction; and e. optionally, separating oligomers from one or more co-products of the reaction.

4. A process for photoreforming plastic waste in a reactor containing a light absorbing carbon enabler, the process comprising the steps of: a. introducing a plastic from plastic waste into the reactor;b. mixing the plastic from plastic waste and the light absorbing carbon enabler to form a mixture; c. exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; d. optionally, separating the hydrogen from one or more co-products of the reaction; and e. optionally, separating oligomers from one or more co-products of the reaction.

5. A process for photoreforming plastic waste in a reactor containing a light absorbing carbon enabler, the process comprising the steps of: a. arranging the light absorbing carbon enabler into sheets by pressing or embedding the carbon enabler into a thermally and light resistant substrate; b. depositing a plastic from plastic waste to contact the light absorbing carbon enabler; c. exposing the mixture to a light source at ambient conditions for a period of time sufficient for the plastic and light absorbing carbon enabler to react with each other to produce a mixture of reaction products comprising hydrogen gas, monomers and oligomers; d. optionally, separating the hydrogen from one or more co-products of the reaction; ande. optionally, separating oligomers from one or more co-products of the reaction.

6. The process according to any one of claims 1 to 5, wherein the plastic comprises a pure olefinic plastic or a mixture of different olefinic plastics.

7. The process according to claim 6, wherein the pure olefinic plastic is polyethylene, polypropylene, polybutylene, polystyrene, polymethylpentene, all isomers of polyethylene, all isomers of polypropylene, all isomers of polybutylene, all isomers of polymethylpentene, co-polymers thereof, or mixtures thereof.

8. The process according to claim 6, wherein the mixture of olefinic plastics comprises two or more of polyethylene, polypropylene, polybutylenes, or polystyrenes.

9. The process according to any one of claims 1 to 5, wherein the oligomers are short-chain oligomers, preferably methane, ethane, propane, butane, pentane, hexane, and their unsaturated derivatives, saturated isomers or unsaturated isomers thereof.

10. The process according to any one of claims 1 to 5, wherein the plastic is in the form of film, powder, pellets, fibers, micro-particles, nano-particles, or combinations thereof.11 . The process according to any one of claims 1 to 5, wherein the plastic is pelletized or shredded.

12. The process according to claim 10 or 11 , wherein a mass ratio of the light absorbing carbon enabler to the plastic is between 1 :1 to 1 :1000.

13. The process according to any one of claims 1 to 5, wherein the light absorbing carbon enabler comprises coal, biomass, carbon black, single walled carbon nanotubes, multi walled carbon nanotubes, biochar, graphene, or graphite.

14. The process according to claim 13, wherein the light absorbing carbon enabler is carbon black.

15. The process according to any one of claims 1 to 5, wherein the light source is located inside the reactor, or outside the reactor.

16. The process according to any one of claims 1 to 5, wherein the light source comprises solar light, a Xenon light source, a light emitting diode (LED) light source, or by other artificial light sources.

17. The process according to any one of claims 1 to 5, wherein the photoreforming of the plastic is carried out under a light intensity ranging from about 5 suns to about 10,000 suns, or less than 100 suns.

18. The process according to any one of claims 1 to 5, wherein the photoreforming of the plastic is carried out under a light intensity ranging from about 0.5 W / cm2to about 50 W / cm219. The process according to any one of claims 1 to 5, wherein the reactor is a continuous stirred reactor or batch reactor.

20. The process according to any one of claims 1 to 5, wherein the process is free from hydrogen, water, or solvents as co-reactants.